Affixation and release assembly for a mill and method

ABSTRACT

A downhole affixation and release assembly including a first component; a second component, and an interconnection device for at least temporarily securing the first component to the second component. The interconnection device operatively arranged to at least partially degrade upon exposure to a fluid. Also included is a method of affixing and releasing two components.

BACKGROUND

In the drilling and completions industry it is common to run a whipstockand a mill in the same run by hanging the whipstock from the end of themill string. Once the whipstock has landed at a selected position andorientation within the borehole, the whipstock is anchored in place andwill bear weight. Because the whipstock is necessarily thinner at theuphole end thereof, it has commonly been a practice in the industry touse a relatively large lug at the uphole end of the whipstock to supporta set down weight from the mill string that is used to separate the millfrom the whipstock, such as by shearing a screw. This arrangementpresents a heavy piece of material that must be removed from the path ofthe mill. Milling the lug often damages the mill due to interruptedcuts, but is nevertheless often performed because of a lack ofalternatives. Accordingly, improvements in affixation and releasearrangements, particularly for mills, are well received by the industry.

BRIEF DESCRIPTION

A downhole affixation and release assembly includes a first component; asecond component, and an interconnection device for at least temporarilysecuring the first component to the second component, theinterconnection device operatively arranged to at least partiallydegrade upon exposure to a fluid.

A cutting assembly includes a mill operatively arranged to cut through awall; a whipstock for directing the mill into the wall, the whipstockincluding an interconnection device for securing the mill to thewhipstock during run-in, the interconnection device operatively arrangedto at least partially degrade upon exposure to a downhole fluid.

A method of affixing and releasing two components includes, affixing afirst component to a second component with an interconnection device;running the first and second components downhole; and degrading theinterconnection device by exposing the interconnection device to afluid.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 is a schematic view of an affixation and release assembly for amill;

FIG. 2 is a schematic view of the assembly of FIG. 1 illustrating themill separated from a whipstock;

FIG. 3 is a schematic view of the assembly of FIGS. 1 and 2 illustratingremoval of a lug via a flow of fluid; and

FIG. 4 is a schematic view of the assembly of FIG. 1 illustrating both alug and a release member being degraded by a flow of fluid.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring now to FIG. 1, an affixation and release assembly 10 is shown,with a mill 12 secured to a whipstock 14 via an interconnection device15. Throughout the Figures, the mill 12 is shown resembling a taperedstarting mill, although it is to be appreciated that other mill types,such as a window mill, could be similarly used. As the end of thewhipstock 14 to which the mill 12 is secured is relatively thin, theinterconnection device 15 includes a lug 16 affixed to the whipstock 14.The interconnection device 15 also includes a release member 18extending through the lug 16 in order to secure the whipstock 14 to themill 12. The releasable member 18 takes the form, for example, of ashear screw, hydraulically actuatable piston or other slidablecomponent, degradable member, etc. The lug 16 is substantially largerthan the end of the whipstock 14 and supports the whipstock 14 in orderto prevent undue distortion of, or damage to, the whipstock 14 whenreleasing the mill 12 from the whipstock 14, due to forces exerted onthe whipstock 14 while positioning the whipstock 14, etc. However, thelug 16 creates an obstacle to the mill 12 that results in an interruptedcutting operation of the mill 12, as the lug 16 is formed essentially ononly one side of the mill 12. The lug 16 can be welded to the whipstock14, secured to the whipstock 14 via the release member 18, etc. The mill12 and the whipstock 14 are installed in an annulus 20 formed by a wall22, which wall could be formed for or by a casing, a borehole, atubular, cement, a combination of the foregoing, etc.

FIGS. 1-3 show one example of how the assembly 10 can be utilized torelease the mill 12. The assembly 10 is shown run in the annulus 20 inFIG. 1, with the mill 12 secured to the whipstock 14 via the releasemember 18 and the lug 16, as described above. The whipstock 14 is set inposition and properly oriented, for example, by use of an anchorassembly or the like (not shown) further downhole in the annulus 20. Thewhipstock 14 can have a known form, e.g., being a tapered for directingthe mill 12 into the wall 22 in order to cut a window or opening in thewall 22. The whipstock 14 could take any other form for, e.g., directingor guiding the mill 12. The mill 12 could similarly take any known formcorresponding to the whipstock 14 in order to achieve a window oropening in the wall 22.

After the whipstock 14 and the mill 12 are in place, e.g., by use of ananchor assembly for the whipstock 14, an event is triggered to releasethe release member 18. For example, if the release member 18 takes theform of a shear screw, applying a set down weight to the mill 12 willshear the release member 18, thereby freeing the mill 12 from thewhipstock 14, as shown in FIG. 2. After release of the member 18, thelug 16 presents a significant obstacle to operation of the mill 12. Thelug 16 is made from a degradable material in order to remove the lug 16from the path of the mill 12 without having to mill the lug 16.“Degradable” is intended to mean that the lug is disintegratable,dissolvable, weakenable, corrodible, or otherwise removable. It is to beunderstood that any use herein of the term “degrade”, or any of itsforms, incorporates the stated meaning. In one embodiment, for example,the lug 16 is degraded by exposure to a downhole fluid, such as water,oil, acid, etc. For example, after release of the member 18, as shown inFIG. 3, a flow of fluid 24, is pumped through the annulus 20 orotherwise delivered to the lug 16 in order to degrade the lug. Inanother embodiment, the mill is hollow or includes a passagetherethrough and the flow of fluid is pumped down the mill string to therelease member 18 or out an opening proximate to the interconnectiondevice 15. Advantageously, degrading the lug prevents the need for themill 12 to remove the lug 16 (or the lug is weakened or reduced in size,resulting in easier removal), thereby avoiding potentially significantwear on the mill 12 and extending the life of the mill. Additionally,since removal of the lug does not have to be accounted for, the mill 12can be more specifically designed to enhance the speed and efficiencywith which the mill 12 cuts through the wall 22.

Alternatively, as shown in FIG. 4, the release member 18 could also bemade from a degradable material, such that the release member 18 is alsodegradable, thereby removing another obstacle, although a relativelyminor one, from the path of the mill 12. In some embodiments including adegradable release member, the release member 18 is not sheared, butinstead, the mill 12 is released from the whipstock 14 by degrading therelease member 18 due to exposure to the flow of fluid 24. In otherembodiments, the degrading process may weaken the release member beforeit is sheared or broken by a set down weight. It is to be understoodthat the same fluid or different fluids could be used to degrade thevarious components. Thus, the release member 18 could be formed by arivet, a bolt, a pin, a rod, a plate, or any other element extendingbetween the whipstock 14 and the mill 12, and could either be eitherintegrally formed with the lug 16 (e.g., an extruded rivet) or formed asa separate component. It is to be appreciated that the lug 16 and therelease member 18 could be utilized to temporarily connect togetherother components in a similar way, with the interconnection device 15(i.e., the lug 16 and/or the release member 18) degrading for enablingrelative movement between the components that was previously preventedby the presence of the interconnection device or a portion thereof.

The interconnection device 15 can be formed from materials that aredegradable by exposure to a variety of fluids capable of being pumped,present, or delivered downhole such as water, acid, oil, etc. Thedegradable material could be a metal, a composite, a polymer, etc., orany other material that is suitably degradable and that can withstandthe loads necessary to initially hang the whipstock 14 from the mill 12during run-in, prevent distortion of the whipstock 14 during loading,etc. However, as described above, it may be possible to avoid very highset down loading by simply degrading the release member 18 after thewhipstock is locked by the downhole anchor assembly, and thus, theinterconnection device 15 may comprise just a release member in someembodiments. In one embodiment, the interconnection device 15, (i.e.,the lug 16 and/or the release member 18) is manufactured from a highstrength controlled electrolytic metallic material and is degradable bybrine, acid, or aqueous fluid.

That is, materials appropriate for the purpose of degradableinterconnection devices as described herein are lightweight,high-strength metallic materials. Examples of suitable materials, e.g.,high strength controlled electrolytic metallic materials, and theirmethods of manufacture are given in United States Patent Publication No.2011/0135953 (Xu, et al.), which Patent Publication is herebyincorporated by reference in its entirety. These lightweight,high-strength and selectably and controllably degradable materialsinclude fully-dense, sintered powder compacts formed from coated powdermaterials that include various lightweight particle cores and corematerials having various single layer and multilayer nanoscale coatings.These powder compacts are made from coated metallic powders that includevarious electrochemically-active (e.g., having relatively higherstandard oxidation potentials) lightweight, high-strength particle coresand core materials, such as electrochemically active metals, that aredispersed within a cellular nanomatrix formed from the various nanoscalemetallic coating layers of metallic coating materials, and areparticularly useful in borehole applications. Suitable core materialsinclude electrochemically active metals having a standard oxidationpotential greater than or equal to that of Zn, including as Mg, Al, Mnor Zn or alloys or combinations thereof For example, tertiary Mg—Al—Xalloys may include, by weight, up to about 85% Mg, up to about 15% Aland up to about 5% X, where X is another material. The core material mayalso include a rare earth element such as Sc, Y, La, Ce, Pr, Nd or Er,or a combination of rare earth elements. In other embodiments, thematerials could include other metals having a standard oxidationpotential less than that of Zn. Also, suitable non-metallic materialsinclude ceramics, glasses (e.g., hollow glass microspheres), carbon, ora combination thereof In one embodiment, the material has asubstantially uniform average thickness between dispersed particles ofabout 50 nm to about 5000 nm. In one embodiment, the coating layers areformed from Al, Ni, W or Al₂O₃, or combinations thereof In oneembodiment, the coating is a multi-layer coating, for example,comprising a first Al layer, a Al₂O₃ layer, and a second Al layer. Insome embodiments, the coating may have a thickness of about 25 nm toabout 2500 nm.

These powder compacts provide a unique and advantageous combination ofmechanical strength properties, such as compression and shear strength,low density and selectable and controllable corrosion properties,particularly rapid and controlled dissolution in various boreholefluids. The fluids may include any number of ionic fluids or highlypolar fluids, such as those that contain various chlorides. Examplesinclude fluids comprising potassium chloride (KCl), hydrochloric acid(HCl), calcium chloride (CaCl₂), calcium bromide (CaBr₂) or zinc bromide(ZnBr₂). For example, the particle core and coating layers of thesepowders may be selected to provide sintered powder compacts suitable foruse as high strength engineered materials having a compressive strengthand shear strength comparable to various other engineered materials,including carbon, stainless and alloy steels, but which also have a lowdensity comparable to various polymers, elastomers, low-density porousceramics and composite materials.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited. Moreover, theuse of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

1. A downhole affixation and release assembly, comprising: a firstcomponent; a second component, and an interconnection device for atleast temporarily securing the first component to the second component,the interconnection device operatively arranged to at least partiallydegrade upon exposure to a fluid.
 2. The assembly of claim 1, whereinthe first member is a mill and the second member is a whipstock.
 3. Theassembly of claim 1, wherein the interconnection device includes a lugsecured to the second component.
 4. The assembly of claim 3, wherein thelug comprises a high strength controlled electrolytic metallic materialand the fluid comprises brine, acid, aqueous fluid, or combinationsincluding at least one of the foregoing.
 5. The assembly of claim 1,wherein the interconnection device includes a release member operativelyarranged to release the first component from the second component. 6.The assembly of claim 5, wherein the release member releases the firstcomponent from the second component by degrading upon exposure to thefluid.
 7. The assembly of claim 5, wherein the release member is a shearscrew.
 8. The assembly of claim 7, wherein the shear screw isoperatively arranged to shear after the second component has landed inan annulus and a set down weight has been exerted on the shear screw viathe first component.
 9. The assembly of claim 8, wherein the releasemember is degradable upon exposure to the downhole fluid.
 10. Theassembly of claim 1, wherein the interconnection device is at leastpartially manufactured from a metal, a composite, a polymer, orcombinations including at least one of the foregoing.
 11. The assemblyof claim 1, wherein the downhole fluid is water, acid, brine, orcombinations including at least one of the foregoing.
 12. A cuttingassembly comprising: a mill operatively arranged to cut through a wall;a whipstock for directing the mill into the wall, the whipstockincluding an interconnection device for securing the mill to thewhipstock during run-in, the interconnection device operatively arrangedto at least partially degrade upon exposure to a downhole fluid.
 13. Theassembly of claim 12, wherein the interconnection device comprises a lugsecured to the whipstock.
 14. The assembly of claim 13, wherein the lugcomprises a high strength controlled electrolytic metallic material andthe fluid comprises brine, acid, aqueous fluid, or combinationsincluding at least one of the foregoing.
 15. The assembly of claim 12,wherein the interconnection device comprises a release member extendingbetween the whipstock and the mill.
 16. The assembly of claim 15,wherein the release member is a shear screw operatively arranged tobreak in response to a set down weight applied to the release member viathe mill.
 17. A method of affixing and releasing two componentscomprising: affixing a first component to a second component with aninterconnection device; running the first and second componentsdownhole; and degrading the interconnection device by exposing theinterconnection device to a fluid.
 18. The method of claim 17, furthercomprising exerting a load on the interconnection device via the firstcomponent to release the first and second components.
 19. The method ofclaim 17, wherein the first component is a mill and the second componentis a whipstock.
 20. The method of claim 19, wherein the interconnectiondevice comprises a lug affixed thereto, the lug being completelydegradable by exposure to the fluid.